This study describes differences in perinatal mortality and age at death in 59 large cities from 1972 through 1981, of rapid change in technology and medical management of high risk pregnancies. It explores whether high rates of neonatal mortality in certain cities can be explained by shifts in mortality from the late fetal to the neonatal period and compares differences in perinatal experience according to age at death by race and city size. A secondary analysis of data sets provided by the National Center for Health Statistics was done based on 100 percent reporting of perinatal deaths. Review of fetal death rates from 24 weeks gestational age and of neonatal deaths for the periods, 1-7, and 8-27 days is being used to examine potential reporting differences among cities and shifting of neonatal deaths into the latter period. These data have not been available publicly for analysis. The analysis provides in improved standard for comparison of perinatal mortality in differing geographic sites.